Americabaetis mecistognathus Salles & Raimundi, 2010

Salles, F. F., Raimundi, E. A., Boldrini, R. & Souza-Franco, G. M., 2010, The genus Americabaetis Kluge (Ephemeroptera: Baetidae) in Brazil: new species, stage description, and key to nymphs, Zootaxa 2560 (1), pp. 16-28 : 17-22

publication ID	https://doi.org/ 10.11646/zootaxa.2560.1.2
DOI	https://doi.org/10.5281/zenodo.5309648
persistent identifier	https://treatment.plazi.org/id/20049746-3C68-FE30-18B9-F9A5FAD9FDFB
treatment provided by	Felipe
scientific name	Americabaetis mecistognathus Salles & Raimundi
status	sp. nov.

Treatment

Americabaetis mecistognathus Salles & Raimundi View in CoL , sp. nov.

( Figs. 1a View FIGURE 1 , 2–13 View FIGURES 2–8 View FIGURES 9–13 , 27 View FIGURES 27–30 )

Diagnoses. Nymphs: 1) frontal keel absent ( Fig. 2 View FIGURES 2–8 ); 2) lingua broadly pointed apically ( Fig. 6 View FIGURES 2–8 ); 3) glossa 0.6x length of paraglossa ( Fig. 8 View FIGURES 2–8 ); 4) apex of paraglossa with rows of pectinate setae ( Fig. 8 View FIGURES 2–8 ); 5) segment II of labial palp with a moderate distomedial projection ( Fig. 8 View FIGURES 2–8 ); 6) posterior margin of abdominal terga with rounded spines ( Fig. 11 View FIGURES 9–13 ); 7) mouthparts unusually elongate ( Fig. 2 View FIGURES 2–8 ).

Adults: unknown.

Description. Nymph. Length of body: 4.0 mm; cerci, terminal filament, and antennae: broken-off in mature nymphs.

Head. Coloration brown. Antenna light brown, scape and pedicel darker.

Lateral branch of epicranial suture curved. Frontal keel absent. Antenna with scape and pedicel subcilindrical. Labrum ( Fig. 3 View FIGURES 2–8 ). Rectangular, longer than broad; length about 1.4x maximum width. Distal margin with medial emargination and small process; dorsally with few short, fine, simple setae scattered over surface. Dorsolateral arc of setae composed of 3 + 2 + 1 long, spine-like setae. Submarginal dorsal row of setae absent. Antero-lateral margin with long, pectinate setae. Ventrally with submarginal row of setae composed of row of short, bifid setae. Ventral surface with short, spine-like setae near anterolateral margin.

Left mandible ( Fig. 4 View FIGURES 2–8 ). Incisors fused; inner and outer set of incisors respectively with 4 + 3 denticles; prostheca robust, apically denticulate and with comb-shape structure at apex. Margin between prostheca and mola straight, with crenulations on distal half, tuft of setae present. Subtriangular process wide, above level of area between prostheca and mola. Denticles of mola not constricted. Tuft of setae at apex of mola present, reduced to a single setae.

Right mandible ( Fig. 5 View FIGURES 2–8 ). Incisors fused; inner and outer set of incisors respectively with 4 + 4 denticles. Prostheca robust, apically denticulate. Margin between prostheca and mola straight; tuft of setae present. Tuft of spine-like setae at base of mola present. Denticles of mola not constricted. Tuft of setae at apex of mola present, reduced to a single setae.

Hypopharynx ( Fig. 6 View FIGURES 2–8 ). Lingua longer than superlingua; apex of lingua broadly acute. Superlingua not expanded; short, fine, simple setae scattered over lateral and distal margin.

Maxilla ( Fig. 7 View FIGURES 2–8 ). Crown of galea-lacinia with 4 denticles; inner dorsal row of setae with 3 denti-setae. Medial protuberance of galea with 4 + 1 simple setae. Maxillary palp 3/4 length of galea-lacinia, with long, fine, simple setae scattered over surface. Palp segment II 1.2x length of segment I.

Labium ( Fig. 8 View FIGURES 2–8 ). Glossa basally broad, narrowing apically and shorter than paraglossa; 0.6x length of paraglossa; inner margin with 7 spine-like setae, outer margin with 6 long spine-like setae increasing in length distally. Paraglossa sub-rectangular; apex with 3 rows of apically pectinate setae. Labial palp with segment I 0,6x length of segments II and III combined; segment I covered with short, simple setae on outer and inner margins and micropores basally; segment II with small distomedial protuberance (distomedial protuberance 0.4x width of base of segment III); inner margin with short simple setae, more numerous at apex; outer margin with few, short, simple setae; dorsally with row of 5 fine and simple setae; segment III conical; length 1,4x width; covered with spine-like and fine, simple setae.

Thorax. General coloration brown with light brown marks.

Foreleg ( Fig. 9 View FIGURES 9–13 ). Coloration brown. Ratio of foreleg 1.4:1.0:0.7:0.3. Forefemur. Length about 3x maximum width; dorsally with row of long blunt setae (in lateral view they look like spine-like setae); (length of setae about 0.1x maximum width of femur). Apex rounded and with blunt setae. Ventrally with short spinelike setae and micropores. Tibia. Dorsally with a row of scarce, short, fine, simple setae; ventrally with one row of spine-like setae. Tibio-patelar suture present. Tarsus. Dorsally with scarce short simple setae; ventrally with one row of spine-like setae. Tarsal claw with one row of 15 denticles. Mid and hind legs similar to foreleg.

Abdomen. General coloration brown. Segments I and IV with posterior medial white mark; distal 2/3 of segment VII and segment X white; segments II to VII with lateral white longitudinal marks; segments II to VI, VIII and IX sublaterally washed with reddish brown ( Fig. 10 View FIGURES 9–13 ). Terga ( Fig. 11 View FIGURES 9–13 ). S urface with abundant scales or scale-bases. Posterior margin with rounded spines. Gills ( Fig. 12 View FIGURES 9–13 ). On segments II – VII. Margin with narrow spines intercalating short, fine, simple setae; tracheae extending from main trunk to inner and outer margins. Paraproct ( Fig. 13 View FIGURES 9–13 ). With 8 marginal spines; surface with scale or scale-bases; postero-lateral extension with minute marginal spines. Caudal filaments. Coloration brown. Terminal filament 0.7–0.8x length of cerci. Posterior margin of segments with short spines on each segment. Inner margin of cercus and inner and outer margin of terminal filament with tufts of long, simple setae.

Comments. Nymphs of the new species were found exclusively at the Rio Chapecozinho ( Fig. 26 View FIGURES 18–26 ), a relatively wide river (around 60 meters) with a riverbed formed by a flat basaltic slab covered in most areas by algae and hydrophytes ( Podostemaceae ) and few allochthonous vegetation. The nymphs were found inhabiting the vertical surface of the riverbed, always associated to hydrophytes and moderate to fast current. The altitude at the type locality is 1031 meters above the sea level (m.a.s.l.).

The new species shares several characteristics with A. titthion and A. labiosus , as the absence of a frontal keel, setae at the apex of paraglossa pectinate, legs robust, spines at the posterior margin of terga blunt to rounded, poorly developed distomedial process of labial palp segment II, and, in the case of A. mecistognathus , sp. nov. and A. labiosus , elongate labium. Nevertheless, in the new species all mouthparts are distinctly elongate. In a general aspect, the mouthparts are nearly as long as the head capsule, which clearly distinguishes A. mecistognathus , sp. nov. from its congeners.

Etymology. From the Greek words mecist, longest, and gnathus, jaws. An allusion to the unusual elongate mouthparts.

Distribution. BRAZIL: Santa Catarina ( Fig. 1a View FIGURE 1 ).

Material examined. HOLOTYPE: Nymph, SANTA CATARINA, Passos Maia, Rio Chapecozinho , S 26°46'1.66" / W 51°49'49.79", 1031 m.a.s.l., 13/iii/2009, pedra em remanso, FFS, EAR cols. ( UFES) GoogleMaps . PARATYPES: same data as holotype [4 nymphs, 2 at CEUNES (one mounted on slides), 2 at INPA] GoogleMaps .